Retinal photoreceptors of albino rats, when exposed to intense, cyclic incandescent, or low intensity, continuous fluorescent illumination gradually undergo severe damage and are destroyed and removed from the eye. Prior to puberty, the photoreceptors are more resistant to photic damage than after adulthood. Concurrent with the onset of pubertal changes, the damage progressively becomes more severe. After ovariectomy of young and adult rats, photoreceptors are more resistant to photic damage than after sham-operation. Hypophysectomy is equally as effective. The objectives of the proposed project are to examine the influence of the pituitary gland and its target organs, through their hormones, on photically-induced and hereditary retinopathies. Synergistic relations between gonadal and pituitary hormones, such as testosterone, estrogen and prolactin will be related to the development of retinal damage. Whether the pineal gland and its amines, serotonin and melatonin, through their influence on gonadal and pituitary functions, are associated with the degree of photoreceptor destruction will be examined in animals after removal of the glands and exposure to continuous illumination.